The treating or refining of metal

ABSTRACT

A method and apparatus for refining iron in which a stream of molten iron is shattered by oxidizing gas in a vessel from which gas is withdrawn to induce air into the vessel.

United States Patent {111 3,554,521

[72] Inventor Malvern John Rhydderch 56 References Cited [2 1] Appl' No.England UNITED STATES PATENTS [22] Filed May 22,1967 2,969,282 l/l961Churcher 75/52X [45] Patented Jam 12 1971 2,995,173 8/1961 Nawalanic239/420X [73] Assignee The R iti h I d Stee] Research 2,997,384 8/1961Feichtmger l64/66X Association 3,174,200 3/1965 Keel et a1 164/66 [32]Priority M33123 1966 3,251,680 5/1966 Goss et a1 266/34(X) Great Britain3,356,489 12/1967 Feichtinger. 266/34X [3]] Nu 22790/66 2,890,953 6/1959Hill et a]. 266/24X 2,951,756 9/1960 Cavanagh 266/25X 3,232,010 2/1966Mahony 266/25X 2 [54] THE TREATING 0R REFINING 0F MET L ,714 1 1/1965Elbl et a1 266/34.1

8 Claims, 4 Drawing Figs. [lint nary [:Zwzmzrter-Jj SfsaergccgrOverholser sszstant xammero n rown [52] [1.8. CI An0mey Ho]c0mbe, w iand Brisebois [51] Int. Cl C2lc 5/28 [50] Field of Search 266/34, 38,ABSTRACT: A method and apparatus for refining iron in 34.1, 34.2, 34PP,34PT, 341', 35, 41, 36P, 36R, 24, 25; 75/51, 52, 54, 59, 60, 46, 93;164/66, 133, 281, 61, 62, 65, 337; 239/420, 422, 29

which a stream of molten iron is shattered by oxidizing gas in a vesselfrom which gas is withdrawn to induce air into the vesse1.

PATENTEDJANIZIQYI 3554521 SHEET 1 UF 2 INVENTOR M .J. R uvnocacuATTORNEYS Pmamammmn 3.5541521 SHEET 2 0F 2 T if 2 III 13a 13a INVENTORM. J. Ruvunenay ATTORNEYS THE TREATING OR REFINING OF METAL Thisinvention is concerned with improvements in and relating to the treatingor refining of carbon-containing metal by oxidizing impurity therein.

In our United Kingdom Pat. Nos. 890,282, 949,610 and 1,006,082, there isdescribed a process for reducing impurity in ferrous metal by oxidizingsuch impurity, the process comprising establishing a stream of moltenmetal and shattering the stream into droplets by a jet of oxidizing gas.This process is referred to as spray refining.

It is an object of this invention to provide an improved spray treatingor refining process and apparatus for carrying out that process.

According to the present invention there is provided a process forrefining molten carbon-containing metal comprising feeding the metal toa reaction vessel as a freely falling flow therein, shattering thefreely falling flow in space within the vessel by streams of oxidizinggas, collecting the refined molten particulate metal in the vessel andextracting gas from the vessel to thereby induce air into the vessel toburn the carbon monoxide produced by the primary oxidation.

Preferably slag forming material is fed to the vessel as a flow adjacentthe metal, the two flows being together shattered and intimately mixedby the gas flow. In the particular case of refining crude iron to reducethe carbon-content, the oxidizing gas is preferably oxygen or oxygenenriched air. The high temperature produced by the oxidation of thecarbon as the gas breaks up the flows renders the slag forming materialmolten and immediate intimate contact is obtained of the refined metaldroplets and molten slag forming material.

According to the present invention there is further provided apparatusfor carrying out the process according to the invention, the apparatuscomprising a container having an outlet from which molten metal may befed as a freely falling flow, a reaction vessel comprising an uppercover portion through which the flow may pass and a lower receivingportion, gas discharge means to produce gas streams convergent upon thepath of the metal flow whereby that flow may be shattered in the vessel,extractor means coupled to the vessel to remove gas therefrom andpassage means communicating between the interior of the vessel andatmosphere through which in operation air will be drawn by the action ofthe, extractor means.

In a preferred form of the apparatus a discharge device for slag formingmaterial is provided to form a curtain of that material which will falladjacent the metal flow to be shattered therewith by the gas flow fromthe gas discharge means.

In order that the present invention may be well understood there willnow be described some embodiments thereof, given by way of example only,reference being made to the accompanying drawing, in which:

FIG. 1 is a diagrammatic cross section of treating or refiningapparatus;

FIG. 2 is a plan view of a gas discharge device;

FIG. 3 is a section on the line Ill-III of FIG. 2; and

FIG. 4 is an elevation of the gas discharge device.

The apparatus for refining metal shown in the drawing is particularlyintended for treating or refining crude iron and comprises a transferladle 1 having a flow control stopper'2 to control molten metal flow toa tundish Shaving a refractory outlet nozzle 4.

Beneath the tundish is a reaction vessel 5 which comprises a cover orhood portion 6, having a central aperture 7 and a gas takeoff 8, and areceptacle portion 9 beneath the hood. An extractor fan 10 is located inthe gas takeoff, which may have a plurality of inlets symmetricallyplaced about the hood por- The tundish nozzle may be circular in sectionnormal to the nozzle axis and the gas discharge outlet, may bean annularmanifold having inwardly and downwardly directed outlets. Such aconstruction is shown and described in our United Kingdom Pat. No.949,6l0.

Alternatively the tundish nozzle has a cross section normal to thedirection of flow of which the dimension of each of two opposite sidesis several times greater than the mean dimension between those sides.For example, the stream may have larger sides of 3 inches and a meandistance between those sides of half an inch. Thus, a streamwill beformed which has a very high surface area-to-volume ratio per unitlength of the stream. v

For shattering such' a stream the 'gas discharge device comprises aheader 12a (FIGS. 2 to 4) having takeoff chambers 14 each having anoutlet 13a which spans the major side of the metal stream which will bepoured and each has a convergent/divergent form in the direction of flowto accelerate the gas during discharge. The outlets may have at the exita smaller dimension of 0.1 inches.

A flux discharge device 16 is mounted above the gas dischargedevice-and-in the case of FIG. 1 comprises an annular manifold 17 havingan inlet 18 and outlets 19 to discharge a curtain surrounding the metalstream. The inlet 18 is coupled to a source of gas entrained flux. Inthe case of FIGS. 2 to 4 the flux discharge device comprises twomanifolds 17a each having an outlet 190 which will form a curtain alongthe adjacent face of the metal stream.

To carry out refining, molten crude iron is withdrawn from a suitablesource into the transfer ladle l and poured at a controlled rate intothe tundish to maintain a constant head in the tundish. The metal in thetundish will fall from the outlet nozzle 4 as a freely falling streamand the rate of flow with a'nozzle passage of /2 by 3 inches with'a headof 14 inches will be 1 ton per minute. The passage may be as large as /2by 24 inches to give a flow for the same head of 8 tons per minute.

The freely falling stream together with curtain streams of gas-entrainedflux on each side discharged from the outlets 19 will be shattered andthe streams of metal and gas-entrained flux will be intimately mixed bythe oxygen discharged from the gas outlets 15. The small particles ofmolten iron present a large surface area to the action of the oxygen andthe flux is rapidly melted by the heat generated and surrounds thesedroplets.

By adoption of thewide thin form of the metal stream the oxygenrequirement for high rates of flow is of the same order per ton of metaltreated as for small flow rates, additional ox ygen merely for'effectingadequate shattering of the stream being unnecessary.

Carbon, silicon, manganese, phosphorus and other impurities in the crudeiron react with the oxygen to form carbon monoxide, silica, manganeseoxide, phosphorus pentoxide and the like. Sulfur is removed as sulfurdioxide and sulfide in the slag which to retain such oxides as silica,manganese oxide, phosphorus pentoxide and the sulfide should be basic.To

' retain phosphorus pentoxide the slag should be oxidizing and the fluxtherefore may be powdered lime or limestone admixed with iron oxide.

During the run of metal into the vessel, the extractor fan 10 operatesto withdraw gas and fume from the vessel and is operated at a rate tocause 'air to be drawn into the vessel through a passage 20 defined bythe hood portion and receptacle portion. This indrawn air will provideoxygen for the combustion of carbon monoxide and thereby the quantity ofoxygen fed to the vessel through the gas discharge outlets is less thanthat which is required to fully oxidize the impurities to bring themetal impurities down to the desired limits.

Large quantities of heat are generated by the reaction and may be usedto melt scrap. This scrap can be placed in the reaction vessel before arun is started. Alternatively or addi' tionally scrap and/or prereducedor partially reduced iron ore may be fed into the reaction vessel bychute 21 during a run either continuously or intermittently. Theaddition of such material during a run is particularly advantageous as atemperature control arrangement and prereduced ore is particularlysuitable since not only is it in suitable form for metering into thevessel, but it is of known composition so that the refined metal can bemade to a'precisely predetermined specification.

A small surplus of air over that required to burn the carbon monoxide isprovided to ensure that no carbon monoxide enquantity of scrap which canbe included is substantially in- Tcreased.

Refining a melt comprising 4.] percent C, 2.3 percent Si,

1.0 percent Mn, 0.05 percent P, 0.05 percent S remainder iron at a rateof 24 tons per hour to a steel of 0.1 percent C, 0.01 percent Si, 0.02percent Mn, 0.02 percent P, 0.02 percent S,

"the rest iron, the quantity of steel scrap melted to provide an endtemperature of 1,650" C. was between 990 and 1,080 pounds for each 2,000pounds of molten iron. The theoretical maximum of scrap was 1,120 poundsfor each 2,000 pounds of molten pig iron. in carrying out this refiningthe quantity of oxygen fed to the gas discharge nozzles was 2,500 cu.ft.per ton of metal and all the carbon monoxide was burnt to leave 1- 2percent oxygen at the extractor inlet, the quantity of indrawn air being7,100 cu.ft./ton of metal.

' The refining process may be a single-stage process or it may beeffected in more than one stage. Thus a first stage spray refining maybe effected to desiliconize and partly decarburize the iron. Thispretreated iron may be further spray refined to remove furtherimpurities in a second stage or may be fed as raw material for steelproduction in another vessel, e.g., an

L.D. converter. In the case of further refining in an L.D. converter,the lower portion of the spray refining vessel of the first stage may bethe LD converter vessel itself located below the hood portion, intowhich alance can be lowered to effect the 'second stage. a

As a further feature of a single stage process, the receiving vessel,after a run, may be agitated as by rotation to bring the reactionfurther toward equilibrium.

instead of a rectangular outlet to form the metal stream a nozzledefining a passage of other cross section may be used to give a highsurface-to-volume ratio per unit length of flow, such for example as anelliptical cross section.

I claim: I

1. Apparatus for treating molten carbon-containing metal comprising acontainer having an outlet from which molten metal may be fed as afreely fallingflow, a reaction vessel comprising an upper compartmentthrough which the metal may pass and a lower receiving compartment, gasdischarge means to direct an oxidizing gas jet into the uppercompartment which intersects and shatters the metal flow, passage meansproviding communication between the upper compartment and the ambientatmosphere when said vessel is in use and so located as to be alwaysabove the metal surface in said vessel, and extractor means for forciblyremoving gas from said upper compartment and thereby'drawing air intosaid upper compartment through said passage means.

2. Apparatus for treating molten carbon-containing metal comprising acontainer having an outlet from which molten metal may be fed as afreely falling flow, a reaction vessel positioned below said containerand comprising an upper hoodvessel, and-extractor means coupled to saidofftake means for forcibly removing gas from said vessel into saidofftake means and thereby drawing air into said vessel via said passage.

3. Apparatus according to claim 1 in which the gas discharge meanscomprises at least one gas discharge outlet which faces inwardly anddownwardly to direct a stream of gas towards the metal flow path.

4. Apparatus according to claim 1 including a discharge device forintroducing slag producing material into the vessel.

5. Apparatus according to claim 4 in which the discharge device ispositioned to discharge slag producing material along a path passingbetween the path of the metal flow and the gas discharge means.

6. Apparatus according to claim 1 in which the vessel includes an inletfor feeding additives thereto during a run.

7. Apparatus as claimed in claim 1 in which said upper compartmentcomprises a hood and said hod and receiving compartment define saidpassage means therebetween.

8. Apparatus according to claim 1 in which the gas discharge meanscomprises at least one gas discharge outlet which faces inwardly anddownwardly and which has a convergent/divergent character to acceleratethe gas flow.

2. Apparatus for treating molten carbon-containing metal comprising acontainer having an outlet from which molten metal may be fed as afreely falling flow, a reaction vessel positioned below said containerand comprising an upper hood through which the metal may pass and alower receptacle, the hood having a downwardly facing rim which defineswith an opposed upwardly facing rim of the receptacle a passage whichplaces the interior of the vessel directly in communication with theambient atmosphere, gas discharge means positioned within the vessel toemit a gas flow to shatter the metal flow, offtake means incommunication with the interior of the vessel, and extractor meanscoupled to said offtake means for forcibly removing gas from said vesselinto said offtake means and thereby drawing air into said vessel viasaid passage.
 3. Apparatus according to claim 1 in which the gasdischarge means comprises at least one gas discharge outlet which facesinwardly and downwardly to direct a stream of gas towards the metal flowpath.
 4. Apparatus according to claim 1 including a discharge device forintroducing slag producing material into the vessel.
 5. Apparatusaccording to claim 4 in which the discharge device is positioned todischarge slag producing material along a path passing between the pathof the metal flow and the gas discharge means.
 6. Apparatus according toclaim 1 in which the vessel includes an inlet for feeding additivesthereto during a run.
 7. Apparatus as claimed in claim 1 in which saidupper compartment comprises a hood and said hod and receivingcompartment define said passage means therebetween.
 8. Apparatusaccording to claim 1 in which the gas discharge means comprises at leastone gas discharge outlet which faces inwardly and downwardly and whichhas a convergent/divergent character to accelerate the gas flow.